This invention relates generally to the field of architectures for networking wireless devices. The wireless devices need not necessarily be computing devices, rather they could also be low bit-rate devices such as elements of a sprinkler control system, a heating, venting and air conditioning (HVAC) system, or security system in a residence, office, or building.
More particularly, this invention relates to a network architecture and method for enabling a plurality of wireless devices to communicate with other wireless devices in a logically defined domain (such as a residence, office building or warehouse), and for enabling such devices to communicate with other devices in higher logically defined domains, such as neighborhood or global networks, including devices on local or wide area Internet Protocol (IP) based networks.
Prior art solutions for networking devices in a residential environment have tended to require expensive, highly complex Ethernet-based network equipment, similar to that found in a commercial setting. Home networking solutions generally have required significant technical expertise to install and manage. Often, the would-be purchaser of the product lacks such expertise, resulting in foregoing purchase of such systems, or experiencing frustration and further expense in getting it to operate properly. This is especially the case in getting the system to interoperate with other networks outside of the residence.
The present invention provides an architecture and technique for connecting a plurality of elements together in a network via wireless, radio frequency (RF) transmission medium. The inventive architecture and method, when carried out with existing and known RF transmission technologies, can be used to provide a significant improvement to prior art user-installed networking solutions.
As will be apparent from the description below, the type of devices or xe2x80x9cnodesxe2x80x9d comprising the elements of the residential or small site network is not particularly important, and can be part of a home computer system, security system, HVAC system, sprinkler system, or any other type of system that involves communication between multiple elements to carry out a particular objective.
In a first aspect, a method is provided for networking a plurality of wireless nodes that are organized into a logical domain. For example, the wireless nodes may be elements of a home security system or an office HVAC, system that are equipped with RF receiver and transmitter circuits. The logical domain may consist of all of the elements of the security system or HVAC system in the building or site where the network is located.
The method is based on a concept of flooding the domain with the packet so that every node in the domain receives the packet, but including in the packet an anti-looping code processed by the nodes that prevents the packet from being rebroadcast by any node in the domain more than once. Thus, the method includes the step of generating a packet in a first node and broadcasting the packet to all the nodes that are in range of the first node. The packet contains, among other things, an anti-looping code. The packet is received by all the nodes in range of the first node, including a second node. The second node re-transmitts or re-broadcasts the packet to all the nodes in range of the second node, including a third node. The de-looping code is processed by the receiving nodes to be sure that the receiving nodes (such as the first node, since it is in range of the second node) broadcast the packet only once.
For example, when the second node re-broadcasts the packet it may be received by a third node in range of the second node but not in range of the first node. The third node will re-broadcast the packet to all nodes in range of it. This flooding process continues until all the nodes in domain have received the packet, with each of the third and additional nodes in the domain processing the anti-looping code to thereby ensure that each of the third and additional nodes rebroadcasts the packet only a single time.
In another aspect, the packet may contain a field containing information uniquely identifying the nodes in a site or logical domain, such that any nodes that may happen to receive the packet which are not located at the site do not respond to the packet. Similarly, the packet can contain information uniquely identifying nodes in a logical sub-network, such that any nodes receiving the packet which are not members of the logical sub-network do not respond to the packet.
As another possibility, the nodes can be organized into multiple hierarchical domains. The packet may comprise a field containing information identifying a domain type, with the domain type indicating the highest domain to which the packet is to be broadcast. Some of the nodes may also function as bridges between one hierarchical domain and another. When such a node receives the packet it inspects the field containing the domain type information, and if the packet is to be broadcast to the domain lying above the node, it broadcasts the packet to nodes in the higher domain. The higher domain may be another RF network, or may be a physical, cabled network, such as a local or wide area Internet Protocol token ring or Ethernet network.
The above-described flooding concept may lead to a possibility of collisions on the RF network between multiple nodes trying to rebroadcast the packet at the same time. We have taken this possibility into account. In still another aspect of the invention, we have provided a method of governing access among a plurality of wireless nodes to an RF wireless communication medium to avoid such collisions. In this aspect, a method is provided for controlling media access of a node in a wireless network to an RF channel by which the node may communicate with other nodes in the network. In the method, if the nodes detect an existing transmission on the RF channel, then their transmission function is disabled. The nodes monitor the RF channel to detect a termination of the existing transmission. The nodes initiate transmission on the RF channel after waiting a random period of time after termination of the existing transmission has occurred. Since each node is waiting a different, randomly-determined period of time before initiating transmission on the RF channel, the chances of collision by simultaneous transmission is greatly avoided. In a preferred embodiment, each of the wireless nodes implements an exponential back off algorithm to arrive at the random period of time before initiating transmission on the wireless network.